1. Field of the Invention
The present invention relates to a process for producing printed substrates on which electric and electronic devices, particularly, components of electric and electronic devices for image-forming apparatus and the like have been patterned. The present invention also relates to processes for producing electron-emitting elements, electron sources and image-forming apparatus using such a process.
2. Related Background Art
The electron emitting element has been heretofore known in two broadly divided types, i.e. the thermoelectron emitting element and the cold cathode electron emitting element. The cold cathode electron emitting element comes in such types as the field emission type (hereinafter referred to as xe2x80x9cFE typexe2x80x9d), metal/insulating layer/metal type (hereinafter referred to as xe2x80x9cMIM typexe2x80x9d), and surface conduction type, for example.
As examples of the FE type electron emitting element, those elements which are disclosed in W. P. Dyke and W. W. Doran, xe2x80x9cField Emission,xe2x80x9d Advances in Electronics and Electron Physics, 8, 89 (1956) or C. A. Spindt, xe2x80x9cPhysical Properties of Thin-film Field Emission Cathodes with Molybdenium Cones,xe2x80x9d J. Appl. Phys., 47, 5248 (1976) have been known.
As an example of the MIM type electron emitting element, the element which is disclosed in C. A. Mead, xe2x80x9cOperation of Tunnel-Emission Devices,xe2x80x9d J. Appl. Phys., 32, 646 (1961) has been known.
As an example of the surface conduction type electron emitting element, the element which is disclosed in M. I. Elinson, xe2x80x9cThe Emission of Hot Electrons and the Field Emission of Electrons from Tin-Oxide,xe2x80x9d Radio Eng. Electron Phys., 10, 1290 (1965) has been known.
The surface conduction type electron emitting element utilizes a phenomenon that flow of an electric current parallel to the surface of a thin film of small area formed on a substrate results in emission of electrons. The surface conduction type electron emitting elements include the element using a thin film of Au reported in G. Dittmer, xe2x80x9cElectrical Conduction and Electron Emission of Discontinuous Thin Films,xe2x80x9d Thin Solid Films, 9, 317 (1972), the element using a thin film of In2O3/SnO2 reported in M. Hartwell and C. G. Fonstad, xe2x80x9cStrong Electron Emission from Patterned Tin-Indium Oxide Thin Films,xe2x80x9d IEEE Trans. ED Conf., 519 (1975), and the element using a thin film of carbon reported in Hisashi Araki et al., xe2x80x9cElectroforming and Electron Emission of Carbon Thin Films,xe2x80x9d J. Vacuum Soc. Japan, Vol. 26, No. 1, page 22 (1983) in addition to the element using a thin film of SnO2 proposed by Elinson as mentioned above.
As a typical example of the surface conduction type electron emitting element, the construction of the element proposed by M. Hartwell et al. as mentioned above is illustrated in the form of a model in FIG. 23. In the figure, 1 denotes a substrate and 4 an electroconductive thin film which is formed of a metal oxide in the pattern shaped like the letter H by sputtering and so forth and made to incorporate therein an electron emitting portion 5 by a treatment of electrification called an energization forming which will be specifically described herein below. As illustrated in the figure, the interval L between element electrodes 2 and 3 is set at a length in the range of 0.5 to 1 mm and the width Wxe2x80x2 of the thin film at 0.1 mm.
In the surface conduction type electron emitting element of this class, the practice of subjecting the electroconductive thin film 4 to the treatment of electrification called energization forming in advance of the emission of electrons thereby forming the electron emitting part 5 thereof has been in vogue. To be specific, the energization forming consists in applying a DC voltage or very gradual elevation of voltage to the opposite terminals of the electroconductive thin film 4 mentioned above thereby forcing this thin film to sustain local fracture, deformation, or degeneration and, as a result, allowing formation of the electron emitting portion 5 in an electrically highly resistant state. The treatment, for example, locally inflicts a fisure to the electroconductive thin film 4 to enable this thin film to emit electrons from the neighborhood of the fisure. The surface conduction type electron emitting element which has undergone the energization forming treatment mentioned above is such that it is enabled to effect emission of electrons from the electron emitting part 5 in response to the application of voltage to the electroconductive thin film 4 and the consequent induction of flow of an electric current through the element.
The surface conduction type electron emitting element of the quality described above enjoys simplicity of construction and allows for the manufacture thereof the use of the conventional technique of semiconductor production. Therefore, applied studies such as a charged beam source and a display device, in which the characteristics of the above-mentioned surface conduction type electron emitting element are utilized, have been performed.
As an example where many surface conduction type electron-emitting elements are arranged, there is an electron source in which surface conduction type electron-emitting elements are arranged in parallel, called a ladder-type arrangement as described below, and connected at the respective ends with wiring (may referred to as common wiring), and many rows of elements thus arranged are arranged in parallel lines (for example, Japanese Patent Application Laid-Open No. 64-031332, Japanese Patent Application Laid-Open No. 1-283749, Japanese Patent Application Laid-Open No. 2-257552, etc.). In recent years, flat-type display devices using liquid crystals have become popular in place of CRT in the field of image-forming apparatuses, such as display devices in particular. However, they have involved such problems that a back light must be provided because they are not self-luminous. There has been a demand for development of a self-luminous type display device. An example of the self-luminous type display device includes an image-forming apparatus which is a display device comprising in combination the above-described electron source, in which many surface conduction type electron-emitting elements are arranged, and phosphors which emit visible light by virtue of electrons emitted from the electron source.
In the production process of an electroconductive thin film in the surface conduction type electron-emitting element according to the above prior art documents, the electroconductive thin film is formed and then patterned by means of photolithographic etching in a semiconductor process. Therefore, large-scale photolithography-etching equipment is essential to the formation of the elements over a wide area. Such a process has thus involved drawbacks that the number of steps is increased, and the production cost is high.
Therefore, as a production process advantageous to a wide area in a production process of a surface conduction type electron-emitting element, it has been proposed in Japanese Patent Application Laid-Open No. 8-171850 to apply droplets of an organic metal-containing aqueous solution onto a substrate by an ink-jet system to form an electroconductive thin film in the desired form without using the photolithographic etching in the step of patterning the electroconductive thin film in the desired form. In this publication, it has also been proposed to coat the substrate with a liquid containing a water repellent prior to the step of applying the organic metal-containing aqueous solution.
It has also been proposed to produce a color filter used in a liquid crystal display device by means of a printing or ink-jet method. The use of the ink-jet method has a possibility that patterning of pixels may be conducted with higher definition compared with the printing method.
It is an object of the present invention to provide a production process of a printed substrate, by which high-definition patterning can be conducted on a substrate.
Another object of the present invention is to provide a process for producing an electron-emitting element having good electron emission characteristics.
A further object of the present invention is to provide a process for producing an electron source having a plurality of electron-emitting elements and improved in evenness of electron emission characteristics between electron-emitting elements.
A still further object of the present invention is to provide a process for producing an image-forming apparatus which can form high-quality images.
A yet still further object of the present invention is to provide production processes of an electron source and an image-forming apparatus, by which yield can be enhanced.
The above objects can be achieved by the present invention described below.
According to the present invention, there is thus provided a process for producing a printed substrate, comprising a step of applying droplets of a liquid containing a material for a desired component to be formed on a substrate to the surface of the substrate to form the component on the substrate, wherein the process comprises, prior to the step of applying the droplets to the substrate surface, a step of subjecting the substrate to a surface treatment in such a manner that the contact angle of the droplet applied with the surface of the substrate falls within a range of from 20xc2x0 to 50xc2x0.
According to the present invention, there is also provided a process for producing an electron-emitting element comprising an electroconductive thin film having an electron-emitting part between electrodes, wherein the step of forming the electroconductive thin film, in which the electron-emitting part is formed, comprises a step of applying droplets of a liquid containing a material for the electroconductive thin film to a substrate, on which a pair of electrodes has been arranged, so as to extend over the electrodes, and prior to the step of applying the droplets, a step of subjecting the substrate to a surface treatment in such a manner that the contact angle of the droplet with the surface of the substrate falls within a range of from 20xc2x0 to 50xc2x0.
According to the present invention, there is further provided a process for producing an electron source in which a plurality of electron-emitting elements each comprising an electroconductive thin film having an electron-emitting part between electrodes are arranged on a substrate, wherein each of the electron-emitting elements is produced by the process described above.
According to the present invention, there is further provided a process for producing an image-forming apparatus comprising an electron source in which a plurality of electron-emitting elements each comprising an electroconductive thin film having an electron-emitting part between electrodes are arranged on a substrate, and an image-forming member capable of forming images by virtue of irradiation of electrons from the electron source, wherein each of the electron-emitting elements is produced by the process described above.